Effects of dibutyryl cyclic-AMP on cardiac output and myocardial contractility in dogs.

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Abstract
Dibutyryl cyclic[c]AMP was administered to a group of anesthetized dogs at doses of 5, 10, 20 and 40 mg/kg, and changes in stroke volume, cardiac output and myocardial contractility were observed. Effects of this substance on contractile performance of isolated cardiac muscle were investigated in another group of dogs. Dibutyryl cAMP increased heart rate, stroke volume and cardiac output in a dose-related manner in the range from 5-40 mg/kg. As indices of myocardial contractility. Vmax and maximum dF/dt [change in force with time] were examined. These showed a dose-dependent increase in response to dibutyryl cAMP. In isolated dog hearts, dibutyryl cAMP raised the Vmax of shortening dose-dependently. Total peripheral resistance declined in a dose-related way. Mean arterial pressure and CVP [central venous pressure] dropped slightly without showing dose-dependence. Dibutyryl cAMP apparently produces positive inotropic and chronotropic effects and causes dilatation of the peripheral vessels in dose-dependent manners.